1. Field of the Invention
The present invention relates to a sorting apparatus which reads, for example, surfaces of sheets such as postal matter on which sorting information such as postal codes are written, and sorts the sheets by performing character recognition on read images, and a control method for the sorting apparatus.
2. Description of the Related Art
A conventional sorting apparatus which sorts sheets reads images on sheets, and sorts the sheets by recognizing characters as sorting information indicating sorting destinations from the read images. For a sheet on which sorting information such as a postal code comprising a seven-digit number or the like is written, this apparatus extracts a character area from a read image, and sorts the sheet by recognizing the character in the area.
A sorting apparatus like that described above sorts a plurality of sheets such as sealed letters or postcards while sequentially conveying them on a convey path. For this reason, a sheet like a sealed letter containing a foreign substance may cause a problem in the process of being conveyed in the sorting apparatus. Some conventional sorting apparatus has a mechanism of detecting a foreign substance contained in a sheet and rejecting the sheet (for example, Jpn. Pat. Appln. KOKAI Publication No. 2003-285957). An example of such a mechanism of detecting a foreign substance contained in a sheet is a mechanism provided with a metal detection unit for detecting a metal piece as a foreign substance contained in a sheet.
In the conventional sorting apparatus, however, a tracking letter (such as a transponder letter or vibration letter) having a metal member is rejected by being detected as a sheet containing a foreign substance by the above metal detection unit. In addition, in the conventional sorting apparatus, even a sheet attached with a small metal piece (e.g., a small fastening plate such as a clip) in a fixed state which is unlikely to cause any problem during conveyance is detected as a sheet containing a foreign substance by the above metal detection unit and rejected. In general, a worker needs to manually sort an rejected sheet. When, for example, the worker manually sorts a tracking letter, it is difficult to grasp the overall processing state of a system which sorts sheets by using the tracking letter. In addition, when the worker needs to manually sort sheets which are unlikely to cause any problem, the overall processing efficiency of the above sorting apparatus deteriorates.